Phone number greyed out in facetime.

Hello,

just upgraded to iPhone 5 after my 4 started going wonky. My major problem was my facetime stopped working and the number was grayed out but still had a tick next to it in the settings, my e mail address was still bold black and ticked but I could not use facetime.

Thought the problem was my wonky phone but now I have the same problem in my iPhone5 😕 also when I activated my new phone it said I could be "reached at facetime with this number 00000000000" and said this could be changed in settings later, but I cant figure out how to get my number back in bold black again...any help would be greatly appreciated.

Thank you.